Irregularities in the ground surface and elevation present a problem when installing an underground irrigation system. It is normally desirable to have the sprinkler heads flush with the ground surface. However, with differences in the surface elevation and angle from the main, the risers must be customized to compensate. Solutions to this problem have not been satisfactory, typically causing a requirement for carrying extra parts in the field, increasing installation time, limiting reliability, and introducing leaks.
A common method of addressing the irregular ground problem is to use a semi-flexible riser with multiple threaded sections along its length. After ground preparation, each head that is not level with the ground (higher, lower, or bent) is dug out and the head removed, after which an extension or longer section is installed or the riser cut down as required. If the head is bent or out of alignment, a rock is jammed on the side of the riser to effect the desired orientation (risking damage to the riser). This procedure is time consuming, inaccurate, unreliable, and allows for contaminants (dirt) to be introduced into the system.
Another common method is illustrated in U.S. Pat. No. 1,337,744 to Ballerstedt. This patent discloses an adjustable riser which in one embodiment has a U shaped pipe having ends which are threaded into a T joint and an elbow respectfully or in a second embodiment has three elbows threaded on both ends and a pipe also threaded on both ends. In the second embodiment, one elbow is threaded onto a T of the main and to the pipe at the other end. The other two elbows are threaded together with one threaded to the other end of the pipe. This latter arrangement allows for the universal head adjustment as with the present invention. However, this system, due to its need for assembly after connection to a T of the main, increases part count and assembly time in the field. The joints involved are also not leakproof due to the need to leave them loose enough to allow for rotation into the desired position (or by virtue of such positioning).